Cover having a thick window for photoelectric unit

ABSTRACT

A cover for a photoelectric unit which is placed over the unit to allow light to strike the photoelectric unit from a single direction. The cover comprises a transparent window having a plurality of tapered extensions at its edges, the extensions emanating from a portion of the thickness of the windowpane. An opaque body member is molded about the window so that portions of the body member cover both sides of the tapered extensions on the windowpane. The thickness of the walls of the body member is substantially less than that of the windowpane.

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[72] Inventor Alvah A. Ruse", Jr- [56] References Cited Glmonbury, UNITED STATES PATENTS 2| App]. No. 822,596

1,764,368 6/1930 Thomas... 250/239 533 1 16 232 3,401,269 9/1968 Tabet 250/239 [73] Assignee mifl'cycompmy Inc 3,5l4,l88 5/1970 Blosse eta]. 35o 319x Middletwon, Conn. Primary Examiner-James W. Lawrence Assistant ExaminerT. N. Grigsby Alt0rneyDeli0 & Montgomery ABSTRACT: A cover for a photoelectric unit which is placed [54] COVER HAVINGATHICK WINDOW FOR over the unit to allow light to strike the photoelectric unit $5 2. p; from a single direction. The cover comprises a transparent g window having a plurality of tapered extensions at its edges,

[52] U.S.Cl 250/239, the extensions emanating from a portion of the thickness of 350/319 the windowpane. An opaque body member is molded about [5 1] Int. CL G02b 5/00, the window so that portions of the body member cover both G02b 7/00,H0li5/02 sides of the tapered extensions on the windowpane. The

[50] Field of Search 250/239; thickness of the walls of the body member is substantially less 350/319, 246, 252 than that of the windowpane.

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PATENTED AUG 2 0 I97! 3 7 k C Jill I NIL l1 i Mm I l I l I I I 5 2 .m m a.

COVER HAVING A THICK WINDOW FOR PI-IOTOELECTRIC UNIT This invention relates to photoelectric covers and, in particular, to photoelectric covers for street lighting photoelectric units.

Photoelectic units usually require covers of one type or another so that the unit will be protected from damage, while 1 allowing light to reach the photoelectric unit. The cover must be constructed inexpensively, but of sturdy material, so that it protects the photoelectric unit from weather conditions.

It has been found that if the cover is completely transparent in all directions, the photoelectric unit may be triggered by stray light, such that the street lights are turned on and off continually. For this reason, the typical cover for a photoelectric street-lighting unit comprises an opaque cover having a transparent window. The most economical method for making such covers, is to mold them from thermosetting plastic. In the construction of such covers, the window is molded and the opaque cover is then molded about the window. An example of this type ofcover is disclosed in U.S. Pat. No. 3,401,269. In that patent, a window pane with a flange formed on allof its sides is first molded. The pane has two adjacent lugs on its upper inside face. The lugs fit into grooves in a male die to maintain the window in place while the cover is being molded about the pane. In a cover of this type, the thickness of the windowpane and the walls of the opaque cover have to be the same. This cover, as wellas the method of making it, has numerous disadvantages. The window is difficult and expensive to construct with the lugs on the inner surface as well as the flanges on all of its edges. Additionally, the window is very difficult to keep in position on the male die with just the lugs for support. Furthermore, with this type of construction, the windowpane must have the exact same thickness as the walls of the cover and, as a result, the thickness of the window is relatively thin. Thus, when it is desired to mold neutral filler into the window to attenuate light transmission through the window, it is very difficult to properly distribute the filler in a thin window. Additionally, with a thin windowpane, the outer surface of the pane must be convex and the inner face ofthe pane concave to conform to the shape of the cover.

Another disadvantage of a windowpane having lugs thereon, is that the rate at which the covers are formed is decreased, due to the fact that the panes with lugs thereon must be positioned in a specific manner on the male die.

A more important disadvantage of a cover of the type disclosed in the aforementioned patent, is that a specific die must be used to form the windowpanes for a particular set of dies which mold the cover so the pane will properly fit in the dies. If the pane is too thin, flashing will occur when the cover is formed. On the other hand, if the pane is too thick, the dies will not be able to close sufficiently to prevent leaks.

In view of the foregoing, it is an object of this invention to provide a new, improved and less expensive cover for a photoelectric unit.

Another object of the invention is to provide new and improved covers for photoelectric units by a more efficient pro-..

Yet another object of this invention is to produce new and improved covers for photoelectric units by a simpler and more I economical process.

Still further objects and advantages of the invention will in part be obvious and will in part appear hereinafter.

In accordance with this invention, an opaque cover for a photoelectric unit is provided, in which the cover has a transparent windowpane which allows light to strike the photoelectric unit from a single direction. The pane is formed with plurality of tapered extensions at its edges over a portion of the thickness of the pane. An opaque body member is molded about the windowpane so that parts of the body member cover both sides of the tapered extensions. The thickness of the walls of the body member is substantially less than that of the windowpane. The windowpane has no obstructions or projections on either of its faces and the external surface of the pane is flush with the external surface of the body member.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others and the method and article possessing the features, properties and relation of elements which are exemplified in the following detailed disclosure and the scope of the 0 invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference is had to the following description taken in connection with the accompanying drawings, in which FIG. 1 is an external view of the cover of this invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a sectional view of the female die and a front view of the male die used to form the cover of this invention.

FIG. 5 is a front partial view of the male die used to form the cover, showing the groove in which the windowpane is positioned; and

FIG. 6 is a cross-sectional view of the male die, indicating the windowpane positioned in the groove in the male die.

Referring generally to FIGS. 1-6, the cover of the present invention comprises a transparent window 11 positioned in the side of an opaque cylindrical body member 12 having a spherical top 13 and cylindrical sides 14. At the bottom of body member 12 and, preferably, formed integrally therewith, is a cylindrical skirt 15. The skirt 15 is not necessary to the present invention. It is desirable that the photoelectric cover have a lower dependent skirt thereon to prevent moisture from seeping through the bottom of the body member and contacting the photoelectric unit within. Thus, the skirt portion 15 will fit about a base member on which the photoelectric unit is located to prevent the seepage of moisture or dirt into the cover. It is to be understood that the skirt portion 15 may have any appropriate design other than that shown in the figures.

It should be noted that the sides of body member 12 are shown as cylindrical in form, although they may be of any other form, such as rectangular. Additionally the top of body member 12 is shown as spherical, since this type of surface has superior strength. However, in accordance with this invention, the top may be ofa flat configuration.

There is also formed, preferably integrally with the body member, internal ribs 17 which may be bored for receiving screws positioned on a base member to secure the body member to the base member. Usually, three such ribs are sufficient for securing the body member to the base member. Directly opposite ribs 17 and on the external side of the body member, are formed indentations 19 which not only permit the use of less material to form the body member, thus making it less expensive but, also, add strength to the body member. It should be understood, however, that, in accordance with this invention, the body member need not have any indentations on it external surface. Any other design may be used for body member 12 which permits the forming of the cover in accordance with this invention.

For the purposes of understanding the advantages of windowpane 11, reference should be made to the manner in which the cover of this invention is constructed. FIGS. 4-6 illustrate the dies in which the cover is formed. The window, body member and skirt are all formed from a thermosetting plastic material. The body member and skirt are formed from opaque thermoplastic such as Lucite, or acrylonitrile butadiene styrene polymers. (Lucite is the trademark for methacrylate ester polymers and can be rendered opaque by adding coloring matter.) The windowpane can be formed from a transparent thermoplastic such as Lucite. The dies for forming windowpane 11 are not shown since they are well known in the art and are not directly pertinent to this invention. The transparent window is formed such that it has a substantial thickness of at least one sixty-fourth of an inch greater than the wall 14 thickness of the cover into which it will be molded. The total thickness of the windowpane may be as much as one-half inch or more, depending on the application for which the cover will be used. The windowpane is formed with tapered extensions on a plurality ofits edges. With the use of a rectangular window, there need be only tapered extensions in the upper and lower edges. However, to obtain as strong ajunction as possible between the window and the sides 14 of the body member, the tapered extensions are on all sides of the windowpane. It was found that V-shaped tapered extensions resulted in the strongest joint between the cylindrical sides and the windowpane. With this type ofjoint, it is impossible to knock the pane from its position without breaking the cylindrical sides. As illustrated in the drawings, the window has a square cross section. However, rectangular, circular, or any other configuration, may also be used. The tapered extensions on the edges of the windowpane are located on only a portion of the thickness of the windowpane. In accordance with this invention, the thickness of the windowpane extends substantially beyond that portion on which tapered extensions 20 are located. The potion 21, extending into the internal side of the cover, is necessary in order for the cover to be molded about the window in accordance with this invention.

Referring particularly to FIG. 4, the female die 22 has a cavity 23 in the shape of the cylindrical sides and spherical top of the body member along with the skirt portion of the cover. There are projections 24 in the female die for forming the indentations 19 on the cover. The opening 25 at the top of the die is used to introduce liquid plastic into the die. The female die also has guide channels 26. The male die 27 has a base plate 28 on which skirt-forming member 29 and guide members 30 are mounted. Body-forming member 31, positioned on top of skirt-forming member 29, has longitudinal grooves 32 therein approximately placed with respect to projections 24, to form ribs 17. Broad groove 33 in the body-forming member 31, extends from a point on the die on which it is desired to position the window pane in the cover. The groove 33 has the same width as the extending portion 21, such that the extending portion 21 of the windowpane fits into the groove. To obtain a good fit, it is desireable for the extending portion 21 to have an edge which is substantially perpendicular to the inner face 34 of the window pane. The extending portion 21 must have a thickness of at least one sixty-fourth ofan inch in order for the window to be properly supported in the male die. However, a thickness of one thirty-second of an inch is preferred. Thus, the groove would be one thirty-second of an inch in depth for such a window.

The groove in the male die must have a uniform depth which is the same as the thickness of extending portion 21. The walls 14 and top 13 of the body member preferably have a thickness ofthree thirty-seconds of an inch since this results in a cover having good tensile strength. However, the cover may have thicker walls. Irrespective of the thickness of the walls of the body member, however, the windowpane must always have a thickness in excess of that of the walls, of at least one sixty-fourth of an inch and, preferably, one thirty-second of an inch so that it may be positioned on the male die. When the body member has a wall thickness of three thirty-seconds of an inch, the portion of the windowpane having tapered extensions 20 will also have a thickness of three thirty-seconds of an inch. The extending portion of the windowpane which fits into the groove may then, preferably, have a thickness of one thirty-second of an inch, or as thick as one-fourth of an inch or more, depending on the application for which the cover will be utilized. This method of positioning the window in the male die is highly superior to that ofthe prior art. One advantage is that the window is not defaced with lugs on its surface which not only prevents the proper transmission of light but, also, makes the window difficult and expensive to manufacture. Further, the support provided to the window in the male die is much better than that provided in the prior art, such that it is difficult to displace the window from the groove, Further, the absence of lugs or projections facilitates the placing of the windowpane in the die, since the window does not have to be inserted in a particular position in the die.

Another very important advantage is that, with the present invention, the windowpane may be molded from a single die for a whole series of cover dies. The grooves in the male dies of the different sets of dies may be machined so that a windowpane, molded from a single die, will fit into all the grooves and bear accurately against the female die. In the covers of the prior art, a different windowpane had to be molded for each set of dies because of the variations in distance between the male and female dies in the area adjacent the windowpane, as indicated by arrows 16 in FIG. 6. In the present invention, the grooves in the dies are machined so that the distance between arrows 18 as indicated in FIG. 6 is the same for different sets of dies.

After the window is placed in groove 33, the male die is moved into the female die so that guide members 30 pass through channels 26 until base 28 fits snugly against the female die to close the bottom of cavity 23. The opaque ther moplastic material is then introduced into the dies through opening 25 to mold the cover. After the cover has been molded, the male die is retracted and the molded cover is easily removed from the male die. Since groove 33 in the male die extends above the windowpane to the top of the male die, a broad rib 35 will be formed on the internal side of the body member directly above the window. The surface 24 of the rib is flush with the internal surface 34 of the window pane. This extension of the groove in the male die permits the easy removal of the formed cover from the male die.

The thick window used in this invention has several unique advantages: it is much easier to uniformly distribute neutral filler into the window to attenuate light transmissivity. The shape of the internal and external surfaces of the window may also be varied with a thicker windowpane. In the cover of the preferred embodiment of the invention, the windowpane is preferably molded with a convex outer surface and concave inner surface, as viewed in FIG. 6, such that it conforms to the shape of the cylindrical sidewalls 14 of the cover. However, when a thick windowpane is used in accordance with this in vention, the outer surface of the pane may also be molded concave as long as there is maintained a rim along the periphery of the external surface of the windowpane in order to prevent the plastic material from flashing onto the concave surface. Also, the internal surface of the windowpane may be made convex, again by maintaining a rim along the periphery of the internal surface of the window. In this case, the convex surface will have to be formed into the thickness of the windowpane so that the pane can fit into the die. It may be desireable to have the external side of the windowpane concave so that the windowpane can better focus the light upon the photoelectric unit.

It will thus be seen that the objects set forth above, among those made apparent from preceding description, are effi ciently attained and since certain changes may be made in carrying out the above method and in the article set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It should also be understood that the foregoing disclosure is intended to cover all the generic and specific features of the invention herein described.

What is claimed is:

l. A cover for a photoelectric unit which is placed over said unit to allow light to strike the photoelectric unit from a single direction, comprising a. a transparent windowpane having a tapered extension on a plurality of the edges of its exterior surface, the

thickness of said extension being less than the total thickness of said pane at its edges, and

b. an apertured opaque body member as a hood for said photoelectric unit, wherein the tapered extension of said windowpane is mated with the edges of said aperture to form a smooth joint therebetween, and wherein the thickness of the bottom an side edges of the aperture of said body member is substantially less than the total thickness of said windowpane at its edges.

2. The photoelectric cover of claim 1, wherein said windowpane is smooth over each of its faces.

3. The photoelectric cover of claim 1, wherein either a said windowpane is concave,

4. The photoelectric cover of claim 1, wherein either face of said window pane is convex.

5. The photoelectric cover of claim 1, wherein the thickness of said windowpane is greater than the thickness of the walls of said body member by at least one sixty-fourth of an inch.

6. The photoelectric cover of claim 1, wherein the external surface of said windowpane is flush with the adjacent outer surfaces of said body member, and wherein the internal surface of said windowpane protrudes from the internal surfaces of said body member.

7. The photoelectric cover of claim 1, further including a skirt member at the lower end of said body member and formed integrally with said body member.

8. A method for producing an opaque cover having a transparent windowpane, which is used to cover a photoelectric unit, comprising a. forming a transparent windowpane, wherein said pane is smooth over each of its faces, wherein said pane has a tapered extension on'a plurality of the edges of its exterior surface, the thickness of said extension being less than the total thickness of said windowpane at its edges,

face of b. positioning the pane in a groove in a male die, such that one entire face of the pane is in the groove, wherein the portion of the pane having a thickness greater than the thickness of the tapered extension projects above the male die,

c. locating said male die within a female die, such that the female die abuts the external surface of said windowpane, and

d. molding an opaque cover about the windowpane, such that portions of the cover mate with the tapered extension of the pane, and wherein the thickness of the walls of said opaque cover is substantially less than the total thickness of said windowpane at its edges.

9. A method in accordance with claim 8, wherein the transparent windowpane is formed such that both faces of said pane are concave.

10. A method in accordance with claim 8, wherein the groove in the male die extends to the upper end of the male die, such that when the cover is molded there is also formed a broad rib on the inner surface of the cover adjacent the upper side of the windowpane and such that the surface of the broad rib is flush with the inner surface of said windowpane to permit easy removal of said cover from the male die. 

1. A cover for a photoelectric unit which is placed over said unit to allow light to strike the photoelectric unit from a single direction, comprising a. a transparent windowpane having a tapered extension on a plurality of the edges of its exterior surface, the thickness of said extension being less than the total thickness of said pane at its edges, and b. an apertured opaque body member as a hood for said photoelectric unit, wherein the tapered extension of said windowpane is mated with the edges of said aperture to form a smooth joint therebetween, and wherein the thickness of the bottom and side edges of the aperture of said body member is substantially less than the total thickness of said windowpane at its edges.
 2. The photoelectric cover of claim 1, wherein said windowpane is smooth over each of its faces.
 3. The photoelectric cover of claim 1, wherein either face of said windowpane is concave.
 4. The photoelectric cover of claim 1, wherein either face of said window pane is convex.
 5. The photoelectric cover of claim 1, wherein the thickness of said windowpane is greater than the thickness of the walls of said body member by at least one sixty-fourth of an inch.
 6. The photoelectric cover of claim 1, wherein the external surface of said windowpane is flush with the adjacent outer surfaces of said body member, and wherein the internal surface of said windowpane protrudes from the internal surfaces of said body member.
 7. The photoelectric cover of claim 1, further including a skirt member at the lower end of said body member and formed integrally with said body member.
 8. A method for producing an opaque cover having a transparent windowpane, which is used to cover a photoelectric unit, comprising a. forming a transparent windowpane, wherein said pane is smooth over each of its faces, wherein said pane has a tapered extension on a plurality of the edges of its exterior surface, the thickness of said extension being less than the total thickness of said windowpane at its edges, b. positioning the pane in a groove in a male die, such that one entire face of the pane is in the groove, wherein the portion of the pane having a thickness greater than the thickness of the tapered extension projects above the male die, c. locating said male die within a female die, such that the female die abuts the external surface of said windowpane, and d. molding an opaque cover about the windowpane, such that portions of the cover mate with the tapered extension of the pane, and wherein the thickness of the walls of said opaque cover is Substantially less than the total thickness of said windowpane at its edges.
 9. A method in accordance with claim 8, wherein the transparent windowpane is formed such that both faces of said pane are concave.
 10. A method in accordance with claim 8, wherein the groove in the male die extends to the upper end of the male die, such that when the cover is molded there is also formed a broad rib on the inner surface of the cover adjacent the upper side of the windowpane and such that the surface of the broad rib is flush with the inner surface of said windowpane to permit easy removal of said cover from the male die. 